1. Field of the Invention
The present invention relates to a liquid ejection head. More particularly, the present invention relates to a liquid ejection head that can suitably be utilized in the technical field of inkjet recording.
2. Description of the Related Art
The thermal system and the piezo system are well known for methods of ejecting liquid by means of liquid ejection heads. With the thermal system, liquid is heated to boil and bubble and the force of the bubbling liquid is employed to eject liquid. With the piezo system, on the other hand, the force by deformation of a piezoelectric element is employed to eject liquid. A liquid ejection head with these systems is formed by laying a plurality of recording element substrates, each having one or more of liquid ejection ports and liquid ejection means, on respective support members, each having one or more than one liquid chambers formed in the inside thereof, regardless if the liquid ejection head is based on the thermal system or on the piezo system. If air bubbles are left in a liquid chamber, the air bubbles may move to an ejection port of the corresponding recording element substrate in an operation of ejecting liquid to give rise to faulty ejections.
As an exemplar solution for the above identified problem, Japanese Patent No. 3,228,569 proposes an arrangement of providing the inner wall of each liquid chamber with a groove while making the width of the liquid chamber narrower at and near the corresponding recording element substrate than the remaining part of the liquid chamber to produce a constricted part in the liquid chamber. With this arrangement, bubbles, if any, in a liquid chamber can be trapped within the liquid chamber and liquid is reliably fed to the corresponding recording element substrate by way of the groove.
In recent years, line heads have been getting popularity for commercial recording applications of liquid ejection heads. Line heads are liquid ejection heads having a width as long as the width of the recording mediums to be used with the liquid ejection head. In a line head, a large number of ejection ports from which liquid is ejected are arranged highly densely than ever. In general, a line head is formed by arranging a plurality of recording element substrates on respective support members that are by turn arranged on a base substrate. In commercial recording applications, line heads are required with high reliability to provide a high recording speed and an image quality above a certain quality level at the same time. Therefore, occurrences of faulty ejections due to air bubbles as mentioned above are far from being desirable.
However, when the arrangement of Japanese Patent No. 3,228,569 is adopted to line heads for commercial recording applications, each of the liquid chambers in a line head is inevitably made small because a very large number of recording element substrates need to be arranged in the line head so that each liquid chamber can hardly secure a space for trapping air babbles in the inside thereof. Additionally line heads that are designed to operate for high speed recording eject a large volume of liquid in a short period of time so that liquid flows at high speed in the liquid chambers of the line head. Then, the air bubbles that are once trapped in a liquid chamber can be pushed toward a corresponding ejection port to give rise to faulty ejections.